The present invention relates to substrate-selecting equipment for a photomask used for the production of a semiconductor integrated circuit and in particular to substrate-selecting equipment for selecting a substrate used for an objective product from among a group of substrates with photosensitive material layer used for the production of photomasks.
In recent years, the desire for high-integration and high-function has increased for various LSI typified by ASIC as a result of the tendency of electric equipment becoming more efficient, lighter, thinner, shorter and smaller. In a photomask used for the production of a semiconductor integrated circuit, forming patterns of a photomask with high efficiency and high quality has come to be desired.
Heretofore, the production of a photomask is carried out generally through the steps shown in FIG. 8.
First, as shown in FIG. 8(a), a substrate (it is called xe2x80x9cblanksxe2x80x9d) provided with a shielding film or shifter layer 820 made of a metallic thin film such as chromium formed on a transparent substrate 810 by sputtering and others is provided.
Then, as shown in FIG. 8(b), a photosensitive material layer 830 such as a photosensitive resin film, photosensitive resist or merely resist is laminated on a shielding film or shifter layer 820, and then dried by heating to remove any solvent remaining in the photosensitive material layer and to improve the adhesion between the metallic thin film 820 and the transparent substrate 810.
Then, as shown in FIG. 8(c), ionizing radiation 840, such as an EB (Electron Beam), a laser beam, or an X-ray, is applied so as to selectively expose the ionizing radiation 840 into a desired pattern. Generally, the ionizing radiation 840 is selectively exposed by the fixed equipment according to pattern data for the formation of the pattern. Therefore, it is also called xe2x80x9cpattern writingxe2x80x9d or merely xe2x80x9cwritingxe2x80x9d.
Then, as shown in FIG. 8(d), the photosensitive material layer 830 is developed to form a resist pattern 835. Thereafter, as shown in FIG. 8(e), areas of the shielding layer 820 made of the metallic thin film exposed within the openings 836 of the resist pattern 835 are etched so that shielding layer pattern 825 is formed.
Finally, the resist pattern 835 is removed so that a photomask formed from the shielding layer pattern 825 can be obtained, as shown in FIG. 8(f). Thereafter, inspection and correction of pattern are carried out according to demand so that a desired photomask is obtained.
The quality of photomask produced in the above-mentioned process is greatly affected by the quality of the substrate with a photosensitive material layer employed for pattern writing. Since there are many types of substrates having a photosensitive material layer thereon, the control of substrates having a photosensitive material layer thereon is difficult. Heretofore, the distinction between good products and poor products is carried out according to the regular standard in the inspection in the process of production so that only good products are employed.
However, the specifications of quality for objective products are various, and substrates with photosensitive material layers distinguished as good products are varied in the phase of quality and the sensitivity of photosensitive material layers. Therefore, substrates corresponding to the specifications of objective products are not always selected. Accordingly, there are cases where the influence of the used substrate on the inspection and correction thereof was considerable.
Further, as circuits of semiconductor products such as LSI chips increase in density, the desire for the formation of patterns having higher accuracy and quality has also increased.
It is an object of the present invention to provide a substrate-selecting equipment wherein substrates used for the production of objective products can be successfully selected from among a group of substrates with photosensitive material layers used for the production of photomasks employed for writing of patterns in the process of photomask, particularly from the phase of quality of products.
The present invention is a substrate-selecting equipment for selecting substrates used for objective products from among a group of substrates with photosensitive material layers used for the production of photomask, wherein the substrate-selecting equipment comprises one or more of the defect-registering part(s) for registering the results of the inspection of defects of substrates with photosensitive material layers in database, the photosensitive material layer lot check result-registering part for registering the results of check of lots of photosensitive material layers in database and the substrate-selecting part for selecting substrates used for the production of objective products from among a group of substrates with photosensitive material layers, on the basis of the results of inspection of defects and the results of check of lots of photosensitive materials registered in database.
Further, in the above-mentioned substrate-selecting equipment, the defect-registering part is comprised of the pinhole defect-registering part for registering the results of inspection of pinhole defects of blanks in which photosensitive material layers are not laminated on substrates in database and the foreign substance defect-registering part for registering the results of inspection of foreign substance in database.
Furthermore, the above-mentioned substrate-selecting equipment further comprises the selection standard-registering part for registering the quality standard of substrates which is the standard of selection of substrates in database, wherein the substrate selection part selects substrates used for the production of objective products, on the basis of the information on the results of check of lots of photosensitive material layers and the quality standard of substrates which is the standard of the selection of substrates, according to demand.
Further, the above-mentioned substrate-selecting equipment further comprises the in pattern area existing defect extracting part for extracting defects existing in a pattern area on a photomask. For the substrate produced, defects existing in a pattern area on a photomask are extracted on the basis of the information from the results of inspection of defects of each substrate and on the basis of the information from the results of check of lots of photosensitive material layers registered in database.
Further, the above-mentioned substrate-selecting equipment further comprises the defect probability-calculating part for calculating the probability that no defect happens or the probability that happen in the surrounding part of a pattern of photomask produced or for calculating the probability that no defect happens or the probability that defects happen inside a pattern of photomask produced, corresponding with the patterns of photomask produced every substrate, on the basis of the information on the results of inspection of defects of each substrate and the information on the results of check of lots of photosensitive material layers registered in a database for candidate substrate nominated for candidate of substrate used for photomask to be produced, and wherein the substrate-selecting part selects substrates used for the production of objective products, on the basis of the probability that no defect happens or the probability that defects happen in the surrounding part of pattern every substrate obtained in the defect probability-calculating part, or from the probability that no defect happens or the probability that defects happen over the whole of pattern, according to demand.
Further, in the above-mentioned substrate-selecting equipment, in the defect probability-calculating part, defect areas having the size larger than the size of defects decided considering errors, corresponding to the position of defect on photomask to be produced, are obtained for all the defects in a substrate, and the non-occurrence probabilities that no defect happens in the surrounding part of patterns in the obtained defect areas are obtained for all the defects in a substrate. Further, the product of non-occurrence probabilities for all the defects in a substrate are obtained, wherein the above-mentioned product corresponds to the probability P0 that no defect happens in the surrounding part of patterns on a photomask on a substrate.
In the above-mentioned substrate-selecting equipment, in the defect probability-calculating part, defect areas having the size larger than the size of defects decided considering errors, corresponding to the position of defect on photomask to be produced, are obtained for all the defects in a substrate, and the non-occurrence probabilities that no defect happens inside patterns in the obtained defect area are obtained for all the defects in a substrate. Further, the product of non-occurrence probabilities for all the defects in a substrate are obtained, wherein the above-mentioned product corresponds to the probability P01 that no defect happens over the whole of patterns on a photomask on a substrate.
The above-mentioned probability includes (approximate) probabilities having substantially meanings, which probabilities are calculated by approximate calculation.
Further, patterns on a photomask are formed the steps shown in FIG. 8, wherein ionizing radiation 840 such as an EB (Electron Beam), a laser beam, or an X-ray is applied to photosensitive material layer 830 of substrate with photosensitive material layer so as to selectively expose the photosensitive material layer to the ionizing radiation into a desired pattern by which latent image thereof is formed. Generally, ionizing radiation 840 is selectively exposed by the fixed equipment according to pattern data for the formation of pattern. Therefore, it is also called xe2x80x9cpattern writingxe2x80x9d or merely xe2x80x9cwritingxe2x80x9d and a pattern area on a photomask is also called xe2x80x9cwriting areaxe2x80x9d.
The substrate-selecting equipment of the present invention having the above-mentioned constitution enables the provision of the substrate-selecting equipment in which substrates used for the provision of objective products can be successfully selected from among a group of substrates with photosensitive material layers employed for writing of pattern in the provision of photomask, particularly from the phase of quality of product.
This is achieved by the substrate-selecting equipment for selecting substrates used for objective parts from among a group of substrates with photosensitive material layers used for the production of photomask, wherein the substrate-selecting equipment comprises one or more of the defect-registering part(s) for registering the results of the inspection of defects of substrates with photosensitive material layers in database, the photosensitive material layer lot check result-registering part and the substrate-selecting part for selecting substrates used for the production of objective products from among a group of a group of substrates with photosensitive material layer on the basis of the results of inspection of defects and the results of check of lots of photosensitive material layers registered in database.
The above-mentioned substrate-selecting equipment further comprises the selection standard-registering part for registering the quality standard (it is called also xe2x80x9crankxe2x80x9d) of substrates which is the standard of selection of substrates in database, wherein the substrate selection part can select substrates used for the production of objective products on the basis of the information on the results of check of lots of photosensitive material layers and the quality standard of substrates which is the standard of the selection of substrates, according to demand.
Further, the above-mentioned substrate-selecting equipment further comprises the defect probability-calculating part wherein the probability that no defect happens or the probability that defects happen in the surrounding part of a patterns on photomask produced is extracted corresponding with the patterns of photomask to be produced every substrate, on the basis of the information of the results of inspection of defects of each substrate and the information on the results of check of the lot of photosensitive material layers registered in a database for candidate substrate nominated for candidate of substrate used for photomask to be produced, and wherein the substrate-selecting part can select substrates used for the production of objective products on the basis of the probability that no defect happens or the probability that defects happen in the surrounding part of pattern every substrate obtained in the defect probability-calculating part, or from the probability that no defect happens or the probability that defects happen in the whole of pattern, according to demand.